Embarking on our dark spirits journey

When you think of Trevethan Distillery, it’s most likely that you associate it with a world class producer of London Dry Gin. However, what many may not realise is that we began making our first dark spirit back in 2019 when we produced a special edition Lost Garden Rum for the Lost Gardens of Heligan. We’ve also been quietly maturing single estate brandy that has been in cask since 2021.

These smaller special release projects are all about our longer-term journey into dark and amber spirits and spirit maturation, which will culminate in the release of our first ‘grain to bottle’ whisky in the years to come.

The production process of dark or amber spirits involves a few more stages than our current gin production process. It can be broken down into 3 key steps: mashing and fermentation, distillation (usually 2 or 3 times), and last maturation.

Over the next 2 or 3 years we will be honing our craft and further developing our mastery in each of these steps, in preparation for our hyper-premium Rum and Whisky releases that promise to be nothing short of exceptional. Below our Head Distiller, John Hall explains the journey so far…

Head Distiller, John Hall, of Cornwall's Trevethan Distillery watching the golden rum drain from the cask in his latest journey into dark spirits — Trevethan’s Head Distiller John Hall

Crafting Exceptional Rum: A journey in flavour

Our rum begins its journey with the fermentation process which involves a thick sugary substance called molasses which we mix with water and insert yeast. The yeast begins to consume the sugars present and produce alcohol compounds and “flavour” compounds as a by-product. Through distillation, these components are then separated, keeping what we like and discarding what we don’t. Surprisingly, a significant portion of the flavour of a cask aged dark spirits is imparted during fermentation and distillation, even before it enters a barrel.

Next comes maturation, which is an art form and not an exact science. The flavours and lifecycle of the spirit will depend on many things, but not least where the wood of the cask was grown, what size the cask is, how the cask has been treated during construction, what alcoholic strength the spirit is when it goes into cask, and of course what many mistakenly believe to be the only contributing factor, what liquid has previously resided in the cask.

The distiller’s expertise plays a crucial role in selecting the right cask for their spirit and consider the flavours already created during fermentation and distillation processes and what flavours are wanted to impart to achieve the desired outcome. This requires careful planning, often years in advance, therefore, it is imperative that the distiller understands how different casks and different woods interact with spirit and impart flavour.

This journey is what I have been working on, essentially since we released our first aged product, Honey Oak Gin back in 2017. Fast forward almost 6 years, I am continuing to develop and define my knowledge through brandy production and further still through our special release Rum series for 2023 & 2024.

Triple Oak Rum from Trevethan Distillery — Trevethan Triple Oak Rum

IMparting coffee flavours: Cask Aged Golden rum

Our first special release rum started off as an experiment in how to impart coffee flavour into rum that was subtle and didn’t completely overpower the rums inherent character. This involved distilling the rum with whole coffee beans in the still resulting in some sweet and citrus forward coffee flavours. I wanted to cask age the rum spirit and considered what would enhance the initial fruity rum notes and the vanilla and orange notes of the coffee. I decided on an American oak ex-bourbon cask. American oak tends to offer sweeter vanilla and honey notes with a mellow oak roundness to tie them together. The bourbon that has been in the cask previously would add depth and a sense of age to the spirit. I used 200L barrel casks as I wanted good amount of surface contact with the spirit but not too much that it would age too quickly. The liquid was placed in cask at 63.5% abv and tasted every 3-6 months. After 18 months I felt it had reached its peak, and I had gained a good knowledge of how that cask had interacted with the spirit. The fruit from the rum was now laced with vanilla and floral honey notes, the coffee had mellowed further and now was just a sweet note of chocolate and roasted coffee grounds and the American oak added a slight kick of ginger on the finish. The final result, our Trevethan Cask Aged Golden Rum.

Virgin Cornish Oak blocks which were used in the making of Trevethan Distillery's Triple Oak Rum — Virgin Cornish Oak

Experimenting with Casks: Triple Oak Rum

The next step in my study in maturation was to compare how different types of cask imparted flavour on a spirit and how they could be blended to create additional complexity and balance. I decided our next rum would be aged in different casks with different wood types and then blended. The aim was to see how much of the flavour imparted by the oak was to do with the previous spirit and how much was to do with where the oak had come from. So, I took some ex-oloroso sherry quarter casks; these are only 55 litres in size so there is a higher surface area in contact with the liquid and can impart flavour faster than a larger cask. Then another 200L ex-bourbon barrel cask and finally some of the toasted Cornish oak pieces we use in our Honey Oak Gin. The spirt was in oak for 8 months and the flavour differences between the 3 types of oak are remarkable. The virgin Cornish oak is earthy and spicy with hints of dark fruit. The oloroso sherry has very rich dried fruit and marzipan flavours and the bourbons is much softer vanilla, honey and burnt oak. However, when blended together (in a closely guarded secret secret proportion), the result is an extremely complex and lasting flavour profile that is a very well-balanced representation of all 3 types of wood and cask. This resulted in our second rum, Trevethan Triple Oak Rum. Just 500 bottles of each rum is now bottled for our loyal and sophisticated Trevethan spirit customers.

Join our Dark Spirit Journey

In today's ever-growing "craft" spirit market, it's often challenging for consumers to distinguish between special release rum, whiskies, and gins that are gimmicks designed for quick sales boosts and distilleries genuinely sharing their development processes. At Trevethan Distillery, our commitment is clear - we want to take you on a journey of craftsmanship, innovation, and excellence. With every special release, we invite you to experience our dedication to the art of dark spirits. This is just the beginning of our journey…

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Our Dark Spirits Journey, so far...